1. Field of the Invention
This invention relates to a dielectric capacitor manufacturing method and a semiconductor storage device manufacturing method especially suitable for use in fabrication of a dielectric capacitor using a dielectric film made of a dielectric material with a perovskite type crystal structure and fabrication of a semiconductor storage device having such a dielectric capacitor.
2. Description of the Related Art
Recently, the area of a memory cell was rapidly reduced along with an increase in storage capacitance of semiconductor storage devices. Concurrently, in a capacitor forming a memory cell, efforts are made to ensure a required charge capacitance by employing a three-dimensional complex structure. Under these circumstances, in the attempt of improving the production yield and reducing the steps of the manufacturing process by simplification of the construction, researches are made toward employment of a dielectric capacitor simplified in construction by using a dielectric film with a high dielectric constant. Known as a dielectric film with a high dielectric constant suitable for use as a dielectric capacitor is one having a perovskite type crystalline structure and made of a polycrystalline oxide with a grain size of 20 to 300 nm, approximately.
A conventional technique for making a dielectric capacitor using a dielectric film made of a dielectric material with a perovskite type crystalline structure was configured to first make a dielectric film on a lower electrode in form of a film on a substrate, then anneal the dielectric film to crystallize it, further make an upper electrode on the crystallized dielectric film, and pattern the upper electrode, dielectric film and lower electrode into the form of a dielectric capacitor by etching, using reactive ion etching (RIE) or ion milling.
However, in the case where a dielectric capacitor using a dielectric film made of a dielectric material with a perovskite type crystalline structure was made by the conventional technique, there was the problem that the characteristics of the dielectric capacitor after treatment deteriorated significantly cue to etching of a certain element or shortage of oxygen along the treated surface of the dielectric film during etching by RIE or ion milling. Especially when the area of the dielectric capacitor was reduced below 10 μm2, particularly, several μm2, along with large-scaling of semiconductor memory, there was a tendency toward an increase of the area occupied by individual crystal grains in the dielectric film relative to the entire area of the capacitor, hence a relative increase of influences from damages of individual crystal grains belonging to side wall portions of the capacitor during etching process, an increase of deterioration of characteristics of the dielectric capacitor.
Moreover, in the case where a dielectric capacitor using a dielectric film made of a dielectric material with a perovskite type crystalline structure was made by the conventional technique, there was a tendency toward an increase of the leak current of the dielectric capacitor due to deposition of a certain metal or generation of a conductive oxide on side walls of the dielectric capacitor during the etching process or the subsequent annealing process especially in large-capacity semiconductor memory in which the area of the dielectric capacitor is reduced below 10 μm2, particularly, several μm2, and it was a serious reason adversely affecting the reliability.